CN102820162B - Double-acting high-voltage sulfur hexafluoride circuit breaker and double-acting transmission device thereof - Google Patents

Abstract

The invention relates to a double-action high-voltage sulfur hexafluoride circuit breaker. A double-action transmission device is arranged between the moving contact assembly and the static arc contact. The active rack and the static arc contact rack are provided with a gear that meshes with the two racks at the same time between the active rack and the static arc contact rack; The rib parallel to the active rack is provided with a roller between the rib and the static arc contact rack that rolls and cooperates with the back of the rib and the static arc contact rack at the same time. The lower ends of the active rack and the rib are both Fixedly connected to the moving contact assembly, the moving contact assembly moves back and forth in a straight line, the active rack and ribs are connected through the linkage plate, the active rack drives the rack of the static arc contact through the gear to do reverse movement, the static arc contact The rack is fixedly connected to the static arc contact and drives the static arc contact to move back and forth in a straight line. The invention also relates to a double-action transmission device of a double-action high-voltage sulfur hexafluoride circuit breaker.

Description

A double-acting high-voltage sulfur hexafluoride circuit breaker and its double-acting transmission device

technical field

The invention belongs to the technical field of high-voltage sulfur hexafluoride circuit breakers, and in particular relates to a double-acting high-voltage sulfur hexafluoride circuit breaker and a double-acting transmission device thereof.

Background technique

With the continuous and in-depth research on the structure of the high-voltage sulfur hexafluoride circuit breaker arc extinguishing chamber, people have invented a self-energy thermal expansion high-voltage sulfur hexafluoride circuit breaker on the basis of the single-pressure compressed gas type sulfur hexafluoride circuit breaker arc extinguishing chamber The arc extinguishing chamber of the arc breaker uses the energy of the arc itself to greatly reduce the operating work, which is a big step forward in technology. Even so, due to the current single-pressure and self-energy circuit breaker interrupters, the opening and closing of the dynamic and static contacts are fixed by the static contact end, and the movement of the movable contact end is used to achieve contact with the static contact. Therefore, the stroke of the moving contact is larger during the opening and closing operation, and the opening and closing action time is longer. In addition, the operating work of the circuit breaker operating mechanism is also required to be relatively large.

In order to reduce the operating power and increase the opening speed so that the time required to reach the arc-extinguishing fracture distance can be reduced as much as possible when opening, a double-acting high-voltage circuit breaker has appeared. The moving contact in the arc-extinguishing chamber A double-action transmission device is added between the static arc contact and the static arc contact, so that the static arc contact and the moving contact move synchronously in reverse, that is, the two move in opposite directions when the brake is opened, and the two move toward each other when the brake is closed. Chinese patent document CN101599389B discloses a double-acting self-energy thermal expansion type high-voltage sulfur hexafluoride circuit breaker arc extinguishing chamber with this function, which includes a moving contact mechanism and a static contact installed directly above the moving contact mechanism The head mechanism, the static contact mechanism includes the static main contact, the static arc contact seat and the static arc contact, the moving contact mechanism includes the arc extinguishing nozzle, the moving main contact and the moving arc contact, the moving main contact and the moving arc The contacts correspond to the static main contact and the static arc contact respectively. The arc extinguishing nozzle includes the main nozzle and the inner nozzle coaxially arranged inside and outside, and the moving arc contact is located inside the inner nozzle; The connected push-pull rod drives the shift fork to rotate, and then through the cooperation between the pin shaft connecting the static arc contact and the shift fork and the horizontal pin hole, the static arc contact is driven to move up and down along the vertical guide rail to realize the moving contact and static arc contact. The reverse movement of this kind of double-action transmission device in the form of a shift fork and a guide rail is not only complex in structure and takes up a large space, but also requires high precision in processing and assembly. In addition, the transmission ratio of the fork transmission is not easy to control, making it difficult to control the action time and movement distance of the static arc contact at a constant value, and it is prone to lagging of the static arc contact , the stability of its action time is poor.

Contents of the invention

The object of the present invention is to provide a double-acting transmission device of a double-acting high-voltage sulfur hexafluoride circuit breaker with simple structure and manufacturing process and low cost. At the same time, the present invention also provides a double-action high-voltage sulfur hexafluoride circuit breaker equipped with such a double-action transmission device.

In order to achieve the above purpose, the double-acting high-voltage sulfur hexafluoride circuit breaker of the present invention adopts the following technical scheme: a double-acting high-voltage sulfur hexafluoride circuit breaker, including a static arc contact, a static contact assembly and an energy-relative static contact The moving contact assembly that moves back and forth in a straight line has a double-acting transmission device between the moving contact assembly and the static arc contact. The moving contact assembly drives the static arc contact to move in reverse through the double-action transmission device. The double-action transmission device includes an active rack and a static arc contact rack that are arranged in parallel and extend along the moving direction of the moving contact assembly. Gears for meshing transmission; ribs parallel to the active rack are provided on the back side of the static arc contact rack, and ribs and static arc contact teeth are arranged between the ribs and the static arc contact rack. The rollers on the back of the bar are rolled and matched at the same time. The positions of the rotating shafts of the rollers and the gears are fixed. The upper end of the active rack and the upper end of the rib are connected by a linkage plate, and the active rack drives the rack of the static arc contact through the gear to make a reverse movement, and the rack of the static arc contact is fixedly connected to the static arc contact to drive The static arc contact moves back and forth in a straight line.

A first support for resisting the elastic deformation of the active rack in a direction away from the gear is provided on the back side of the active rack, and a first support member is provided on the back side of the rib for resisting the elastic deformation of the rib in a direction away from the roller The positions of the first and second support members are fixed, the first support member slides or rolls with the back of the active rack, and the second support slides or rolls with the back of the rib.

The first and second support members are support rollers or support rollers, the first and second support members are collinear with the centers of the gears and the rollers, and the line connecting the four centers of circles is perpendicular to the moving direction of the moving contact assembly .

On one or both sides of the gear, there is a guide plate with the plate surface parallel to the gear plane. The guide plate is fixedly installed on the static contact assembly, and the gear is rotatably installed on the guide plate; the upper end of the driving rack is set on the guide The first guide groove on the plate for guiding the linear reciprocating movement of the active rack is guided; the upper end of the static arc contact rack is set on the guide plate for guiding the linear reciprocating movement of the static arc contact rack. Guidance fit; the upper end of the rib is guided and matched with the third guide groove provided on the guide plate for guiding the rib to reciprocate in a straight line.

The upper end of the main nozzle of the moving contact assembly is fixedly provided with a nozzle positioning member, and the lower ends of the active rack and ribs are fixedly connected to the nozzle positioning member; the lower end of the static arc contact rack is fixedly connected to the The upper end of the static arc contact.

The upper end of the main nozzle of the moving contact assembly is fixedly provided with a nozzle positioning member, and the lower ends of the active rack and ribs are fixedly connected to the nozzle positioning member; the lower end of the static arc contact rack is fixedly connected to the The upper end of the static arc contact.

The double-acting transmission device of the double-acting high-voltage sulfur hexafluoride circuit breaker of the present invention adopts the following technical scheme: a double-acting transmission device for a double-acting high-voltage sulfur hexafluoride circuit breaker. The active rack and the static arc contact rack extending in the moving direction of the moving contact assembly are provided with a gear meshing with the two racks at the same time between the active rack and the static arc contact rack; One side of the back of the bar is provided with a rib parallel to the active rack, and between the rib and the static arc contact rack, there is a roller that rolls and cooperates with the rib and the back of the static arc contact rack at the same time, and the roller and the gear The position of the rotating shaft is fixed, the lower end of the active rack and the lower end of the rib are used for fixed connection with the moving contact assembly, and the follow-up contact assembly makes linear reciprocating movement, the upper end of the active rack and the upper end of the rib The parts are connected by a linkage plate, the active rack drives the static arc contact rack to move in reverse through the gear, and the static arc contact rack is used for fixed connection with the static arc contact and drives the static arc contact to do linear reciprocating movement.

A first support for resisting the elastic deformation of the active rack in a direction away from the gear is provided on the back side of the active rack, and a first support member is provided on the back side of the rib for resisting the elastic deformation of the rib in a direction away from the roller The positions of the first and second support members are fixed, the first support member slides or rolls with the back of the active rack, and the second support slides or rolls with the back of the rib.

The first and second support members are support rollers or support rollers, the first and second support members are collinear with the centers of the gears and the rollers, and the line connecting the four centers of circles is perpendicular to the moving direction of the moving contact assembly .

On one or both sides of the gear, there is a guide plate with the plate surface parallel to the gear plane. The guide plate is fixedly installed on the static contact assembly, and the gear is rotatably installed on the guide plate; the lower end of the driving rack is fixed end, used to be fixedly connected to the moving contact assembly, the upper end of the active rack is guided and matched with the first guide groove on the guide plate for guiding the linear reciprocating movement of the active rack; the static arc contact rack The lower end is a fixed end, which is used to be fixedly connected to the static arc contact, and the upper end of the static arc contact rack is guided to cooperate with the second guide groove provided on the guide plate for guiding the static arc contact rack to move back and forth in a straight line; The lower end of the rib is a fixed end for being fixedly connected to the moving contact assembly, and the upper end of the rib is guided and matched with a third guide groove provided on the guide plate for guiding the rib to reciprocate in a straight line.

In the present invention, after the double-moving transmission device between the moving contact assembly and the static arc contact adopts a rack and pinion transmission structure, compared with the existing transmission structure in the form of a shift fork, the overall structure of the transmission device is compact, and the gears, The processing and assembly process of the rack is simple and the precision is easy to guarantee, and the manufacturing cost is reduced; at the same time, the rack and pinion transmits large power, stable transmission, and high reliability. The contact assembly has good synchronization and fast response speed. According to the test, the opening speed of the circuit breaker of the present invention can reach 15m/s, which satisfies the requirements of the circuit breaker on the opening speed, and makes the opening and closing The stability of the action time and the reliability of the opening and closing actions have been strongly guaranteed. In addition, the ribs are connected to the active rack through the linkage plate to form a pull on the active rack, which effectively prevents the elastic deformation of the active rack and the static arc contact rack during the opening and closing movement, ensuring that the gear The effectiveness of rack meshing and the reliability of power transmission, because the ribs and active rack are symmetrically fixed on the main nozzle, the force on the main nozzle is balanced, and the entire motion system moves smoothly.

In the present invention, by setting guide grooves corresponding to each rack and rib on the guide plate, it is convenient to guide the movement of each rack and rib, and the reliable meshing and power of each rack and gear are well ensured. Transmission, at the same time, can also play the role of limit to prevent damage to parts due to overshoot due to excessive speed. By setting the first and second supports, the elastic deformation of the active rack, the static arc contact rack and the ribs is further reduced during the opening and closing movement, and the reliability of the meshing transmission is further improved, thereby improving The reliability and stability of the opening and closing action of the circuit breaker; the two supports adopt the form of supporting rollers or rollers to reduce friction and reduce the loss of operating work.

Description of drawings

Fig. 1 is a schematic structural view of an embodiment of a double-acting high-voltage sulfur hexafluoride circuit breaker of the present invention;

Fig. 2 is the left view of Fig. 1;

Fig. 3 is a perspective view of a half-moon sleeve constituting the spout positioning member in Fig. 1 .

Detailed ways

The embodiment of the double-acting transmission device of the double-acting high-voltage sulfur hexafluoride circuit breaker provided by the present invention is shown in Fig. 1 and Fig. 2. Extended driving rack 6 and static arc contact rack 24, between the active rack and the static arc contact rack is provided with a gear 28 that meshes with the two racks simultaneously, and at the back of the static arc contact rack One side is also provided with the rib 22 parallel to driving rack, between rib and static arc contact rack 24, is provided with the roller 25 that rolls and cooperates with rib and static arc contact rack back side simultaneously, and roller 25 and the position of the rotating shaft of the gear 28 are all fixedly set, the lower end of the driving rack and the lower end of the rib are used to be fixedly connected with the moving contact assembly, and the follower moving contact assembly does linear reciprocating movement up and down, and the upper end of the driving rack The upper end of the upper part and the rib is connected by a linkage plate 34, and the active rack 6 drives the static arc contact rack 24 to perform reverse movement through the gear 28, and the static arc contact rack 24 is used for fixed connection with the static arc contact 21 , Drive the static arc contactor to move back and forth in a straight line.

In this embodiment, both sides of the gear are provided with a guide plate 3 whose plate surface is parallel to the gear plane. The lower ends of the two guide plates are used to be fixed on the arc contact seat 23 of the static contact assembly. A T-shaped spacer 2 is sandwiched between the upper ends, and is connected together through the spacer to ensure the distance between the two guide plates. The protruding part of the T-shaped spacer is located outside the guide plate, and this part can be used Cylinder, square or ball head and other forms are convenient to hold and use during assembly; gear 28 and roller 25 are installed on the two guide plates 3 through their respective rotating shafts; the lower end of the driving rack 6 is a fixed end for fixed connection On the moving contact assembly, the upper end of the driving rack is guided and matched with the first guide groove 31 provided on the guide plate for guiding the linear reciprocating movement of the driving rack through the guide pin 4 provided on it, and the matching form can be sliding Or rolling fit; the lower end of the static arc contact rack 24 is a fixed end, which is used to be fixedly connected to the static arc contact 21, and the upper end of the static arc contact rack is connected with the guide pin provided on it by being arranged on it. The second guide groove 32 on the guide plate for guiding the linear reciprocating movement of the static arc contact rack is guided and matched, and the matching form can be a sliding or rolling fit; the lower end of the rib 22 is a fixed end for fixed connection on the On the movable contact assembly, the upper end of the rib is guided and matched with the third guide groove 33 provided on the guide plate for guiding the rib to move linearly and reciprocally through the guide pin thereon. The two ends of the linkage plate 34 realize the connection with the active rack and the rib through the guide pins on the upper end of the active rack 6 and the rib 22 respectively. The guide pins on the bar are at the same height position, so that the linkage plate is perpendicular to the driving rack and the rib.

On the guide plate 3, on the position corresponding to the back of the driving rack 6, a first support member 5 is installed for resisting the elastic deformation of the driving rack in a direction away from the gear 28; The second supporting member resists the elastic deformation of the ribs in the direction away from the roller 25. Both supporting members are supporting rollers. The first supporting member rolls and cooperates with the back of the driving rack, and the second support rolls and cooperates with the back of the ribs; Simultaneously, the centers of the first and second support members, the gear 28 and the roller 25 are collinear, and the line connecting the centers of the four is perpendicular to the moving direction of the moving contact assembly, that is, perpendicular to the static arc contact rack, like this It can effectively prevent the elastic deformation of the active rack 6 and the static arc contact rack 24 during opening and closing, thereby affecting the reliable meshing and power transmission between the gear and the rack, making the power transmission more stable and reliable, and further increasing the opening and closing action. Time stability and reliability. Of course, if the centers of the four circles are not on a straight line, they can also play a certain role in resisting elastic deformation.

An embodiment of the double-action high-voltage sulfur hexafluoride circuit breaker provided by the present invention is shown in Figure 1-Figure 3, which includes a static arc contact 21, a fixed static contact assembly and a relatively static contact A moving contact assembly that reciprocates linearly, wherein the moving contact assembly includes a moving contact 10 and a main nozzle 18 installed on the moving contact. The upper end of the main nozzle is fixedly connected with a nozzle positioning member 7, and the nozzle positioning member is After the two half-moon-shaped sleeves are relatively fastened on the main spout as shown in Figure 3, they are then tightly hooped on the main spout by means of radial tightening of the fasteners. The cooperation between the main spout and the spout positioning piece The surface is divided into a card slot and a card edge for axial positioning, and the assembly and connection structure of the spout positioning member is simple and easy to install. On the spout positioner 7, a moving end shield 20 is also fixedly installed, and the shield extends downwards to surround the periphery of the main spout mouth. There is an inner spout 17 in the main spout, and a moving arc contact 16 is arranged in the inner spout. The lower end of the moving arc contact is equipped with a pull rod 13, and the whole moving contact assembly is set in the moving contact seat 11 and slides up and down relative to the moving contact seat; the static contact assembly includes the static contact seat 8 and the static contact assembly The static support 1 at the upper end of the head seat, the inner cavity of the static contact seat and the inner cavity of the static support are connected to form a space for the static arc contact 21 and the double-motion transmission to move up and down, and the static contact seat 8 The inner side of the lower end is equipped with a static contact finger 19, and the outer periphery of the lower end is provided with a static end shield 9 installed on the static contact seat. In the static contact seat 8, the static arc contact 21 slides through the In the arc contact seat 23 , the arc contact seat is fixed on the static contact seat 8 .

In this embodiment, a double-action transmission device is provided between the moving contact assembly and the static arc contact of the static contact assembly, and the moving contact assembly drives the static arc contact 21 to perform reverse movement through the double-action transmission device. The structure of the double-acting transmission device provided by the present invention is the same as that of the above-mentioned double-acting transmission device, and will not be repeated here. The guide plate 3 in the double-action transmission device is located in the static support 1, and the lower end of the guide plate is fixedly connected to the arc. The upper end of the contact seat 23, the lower end of the active rack 6 and the lower end of the rib 22 are all fixedly connected to the upper end of the nozzle positioning member 7, and the lower end of the static arc contact rack 24 is fixedly connected to the upper end of the static arc contact 21 .

The opening and closing movement process of this embodiment is as follows: when opening, the pull rod 13 moves downward, driving the moving contact assembly to move downward, and the spout positioning part 7 in this assembly passes through the active rack 6, the gear 28 and the static arc contact. The meshing transmission of the head rack 24 drives the static arc contact 21 to move upward to realize opening; when closing, the pull rod 13 moves upward, and the moving direction of each moving part is just opposite to the opening process, so it will not be described in detail; the opening and closing process Among them, the ribs 22 are synchronously linked with the driving rack 6, both of which are driven by the nozzle positioning member, and the movable end shield 20 is moved together by the nozzle positioning member 7. 12 among Fig. 1, Fig. 2 is movable support, and 14 is the insulation part in the pull rod.

In other embodiments of the present invention, other ways can also be used for the fixed connection of the active rack, the rib and the moving contact assembly. For example, the lower end or the side can be directly fixedly connected to the main spout. At this time, the spout can be omitted. Positioning parts; the supporting rollers in the double-acting transmission can also be in the form of rollers or supporting parts that slide and fit with the back of the driving rack. In the case of meshing, the corresponding support can also be omitted; the guide plate is set for fixing each rack, rib, gear and support. In specific implementation, guide plates can be set on both sides of the gear according to the actual situation. The form of setting a guide plate on one side of the gear is adopted, and the structure of the guide plate is not limited to the plate structure, as long as it can fix the corresponding parts; the guide groove on the guide plate is not necessary, as long as it can Each rack is limited and the limiter that slides with the corresponding rack is enough; if the fixed connection of the lower end of each rack and the cooperation with the gear and the supporting roller can ensure that it can move relatively smoothly, it can also be used at this time. The limit and guide structures are omitted; the gears and supporting rollers can also be installed with other brackets fixed on the static contact seat or the static support.

Claims (9)

1. A double-acting high-voltage sulfur hexafluoride circuit breaker, including a static arc contact, a static contact assembly, and a moving contact assembly that can move back and forth in a straight line relative to the static contact assembly. There is a double-action transmission device between them, and the moving contact assembly drives the static arc contact to move in reverse through the double-action transmission device. The active rack and the static arc contact rack extending in the same direction, there is a gear that meshes with the two racks at the same time between the active rack and the static arc contact rack; on the back side of the static arc contact rack There is a rib parallel to the driving rack, and a roller that rolls and cooperates with the rib and the back of the static arc contact rack is installed between the rib and the static arc contact rack. The positions of the rotating shafts of the roller and the gear are fixed Setting, the lower end of the active rack and the lower end of the ribs are fixedly connected to the moving contact assembly, and the follower contact assembly moves back and forth in a straight line, and the upper end of the active rack and the upper end of the rib are connected by a linkage plate , to prevent the elastic deformation of the active rack and the static arc contact rack during the opening and closing movement, the active rack drives the static arc contact rack to make reverse movement through the gear, and the static arc contact rack is fixedly connected to the static On the contact, the static arc contact is driven to reciprocate in a straight line. The upper end of the main nozzle of the moving contact assembly is fixed with a nozzle positioning piece, and the lower ends of the active rack and ribs are fixedly connected to the nozzle positioning piece. ; The lower end of the static arc contact rack is fixedly connected to the upper end of the static arc contact. 2. The double-acting high-voltage sulfur hexafluoride circuit breaker according to claim 1, characterized in that: a first support for resisting the elastic deformation of the driving rack in the direction away from the gear is provided on one side of the back of the driving rack , on one side of the back of the rib, there is a second support for resisting the elastic deformation of the rib to the direction away from the roller, the positions of the first and second support are fixed, and the first support and the back of the driving rack Slip fit or roll fit, the second support is a slip fit or roll fit with the back of the rib. 3. The double-acting high-voltage sulfur hexafluoride circuit breaker according to claim 2, characterized in that: the first and second supports are support rollers or support rollers, and the first and second supports are connected with gears, The centers of the four rollers are collinear, and the line connecting the centers of the four rollers is perpendicular to the moving direction of the moving contact assembly. 4. The double-acting high-voltage sulfur hexafluoride circuit breaker according to any one of claims 1-3, characterized in that: a guide plate with a plate surface parallel to the plane of the gear is provided on one or both sides of the gear, and the guide plate It is fixedly installed on the static contact assembly, and the gear is rotatably installed on the guide plate; the upper end of the active rack is guided and matched with the first guide groove on the guide plate for guiding the linear reciprocating movement of the active rack; the static arc contact The upper end of the head rack guides and cooperates with the second guide groove on the guide plate for guiding the linear reciprocating movement of the static arc contact rack; The third guide slot guides and cooperates. 5. The double-acting high-voltage sulfur hexafluoride circuit breaker according to claim 4, characterized in that: the upper end of the main nozzle of the moving contact assembly is fixed with a nozzle positioning member, and the active rack and the rib The lower ends are all fixedly connected to the spout positioner; the lower end of the static arc contact rack is fixedly connected to the upper end of the static arc contact. 6. A double-acting transmission device for a double-acting high-voltage sulfur hexafluoride circuit breaker, characterized in that the transmission device includes active racks and static arc contact teeth arranged in parallel and extending along the moving direction of the moving contact assembly Between the active rack and the static arc contact rack, there is a gear that meshes with the two racks at the same time; on the back side of the static arc contact rack, there is a rib parallel to the active rack. Between the rib and the static arc contact rack, there is a roller that rolls and cooperates with the back of the rib and the static arc contact rack at the same time. The position of the rotating shaft of the roller and the gear is fixed. The lower end is used for fixed connection with the moving contact assembly, and the follow-up contact assembly makes linear reciprocating movement. The upper end of the active rack and the upper end of the rib are connected through a linkage plate to prevent the active rack and the upper end of the rib during the opening and closing movement. The rack of the static arc contact is elastically deformed, and the active rack drives the rack of the static arc contact to move in the opposite direction through the gear. The rack of the static arc contact is used for fixed connection with the static arc contact and drives the static arc contact to make a straight line reciprocating movement. 7. The double-acting transmission device of the double-acting high-voltage sulfur hexafluoride circuit breaker according to claim 6, characterized in that: on one side of the back of the active rack, there is a device for resisting the elastic deformation of the active rack in the direction away from the gear. The first support member is provided on one side of the back of the rib to resist the elastic deformation of the rib to the direction away from the roller. The positions of the first and second support members are fixed, and the first support member and The back of the active rack is in sliding fit or rolling fit, and the second supporting member is in sliding fit or rolling fitting with the back of the rib. 8. The double-acting transmission device of the double-acting high-voltage sulfur hexafluoride circuit breaker according to claim 7, characterized in that: the first and second supports are supporting rollers or supporting rollers, and the first and second The centers of the supporting member, the gear and the roller are in the same line, and the line connecting the centers of the four is perpendicular to the moving direction of the moving contact assembly. 9. The double-acting transmission device of a double-acting high-voltage sulfur hexafluoride circuit breaker according to any one of claims 6-8, characterized in that: one or both sides of the gear are provided with a plate whose surface is parallel to the gear plane. The guide plate is fixedly installed on the static contact assembly, and the gear is rotatably installed on the guide plate; the lower end of the active rack is a fixed end, which is used to be fixedly connected to the movable contact assembly. The upper end guides and cooperates with the first guide groove provided on the guide plate for guiding the linear reciprocating movement of the active rack; the lower end of the static arc contact rack is a fixed end for fixed connection on the static arc contact. The upper end of the arc contact rack guides and cooperates with the second guide groove on the guide plate for guiding the linear reciprocating movement of the static arc contact rack; the lower end of the rib is a fixed end, which is used for fixed connection on the moving contact On the head assembly, the upper end of the rib is guided and matched with the third guide groove provided on the guide plate for guiding the rib to reciprocate in a straight line.